1. Field of the Invention
This invention relates generally to an apparatus for crushing materials, and more specifically to a blockage clearing apparatus and method for clearing a blockage during operation of a crushing apparatus.
2. Description of the Related Art
When concrete, asphalt, virgin rock or any other breakable materials need to be reduced in size, a machine referred to as a crusher is used. A crusher is normally mounted on a fixed or portable apparatus called a crushing machine. The materials are poured into the crushing machine in large pieces and are crushed into a smaller, more manageable size. The machine produces a smaller particulate product, which can be recycled and reused for other projects.
A conventional crushing machine, as illustrated in FIGS. 1 to 3, has a hopper 10 with vibrating steel plates 12 to move the crushable materials toward the crusher 14. The hopper 10 receives the materials and has grizzlies 16, which are vibrating steel bars that act as a sieve to separate the smaller materials from the larger materials. The smaller materials are sifted through the grizzlies 16 to reduce wear on the crusher, because already reduced-size product need not pass through the crusher. The smaller particles fall onto a conveyer 18 that moves the small particles out of the machine into a pile beside the machine. If all of the materials need to be crushed, a gate can be used to send all materials through the crusher.
The larger materials move across the grizzlies 16 through an opening 20 into the crusher 14. The crusher 14 has a housing 22 with a lid 24, and the housing 22 contains a rotor 26 with radial blow bars 28a and 28b. Conventional crushers typically have two, three or four blow bars. During operation, the rotor 26 rotates the blow bars 28a and 28b at a rate between about 300 rpm and 800 rpm. The blow bars impact the large, crushable pieces and throw them against at least one anvil 30 for breaking the larger pieces into smaller particles. The anvil and blow bars are made of an extremely tough material, and are readily replaced when worn. Directly beneath the rotor 26 is a vibrating plate, or the conveyer 38, which moves the materials out of the crusher 14 and through the rest of the machine. The crushed materials are moved from the machine into a pile at the end of the machine or into a waiting truck.
One problem with this conventional machine is that large pieces that are placed into the hopper 10 can plug or block the crusher 14 upon entry through the opening 20, or even before entering the opening. Plugging occurs when the material in the hopper backs up due to being arranged in or near the opening 20 in such a way that normal passage to the rotor, where the pieces can be reduced in size, is hindered. When the large materials plug the conventional crushing machine, the rotor has to be turned off in order to free the materials from the crusher, such as by opening the crusher to unplug it, by using vibratory hammers to break up blocking materials, or by using heavy equipment, such as a loader bucket, to move the blocking materials.
Conventional crushing machines include numerous safety features that do not allow the lid 24 of the crusher 14 to be opened while the crusher 14 is in operation. Therefore, the only way to open the lid in a conventional crusher is to stop the rotation of the rotor. Additionally, due to the size and weight of the materials and the crushing machine, a crowbar or backhoe is needed to dislodge the materials from the crusher 14. This process not only slows the progress of the crushing process, it requires additional tools and manpower to free the lodged materials.
Therefore, there is a need for an improved method and apparatus for crushing and for dislodging materials that may plug the crushing machine while in operation.